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Thinning

I am not hugely experienced with freehand stones but I get pretty good results at the minute. However, something I have no experience of is thinning, so I have a few questions for those who are more knowledgeable than me.

The thing I never understand is knowing how much to thin. Do you just basically count strokes on the stone, or use calipers? Another thing. If you thin say the last 3rd of the blade, surely you will not get a burr, so after you have thinned do you just put a bevel on the blade as normal and start again at your usual angle? These are the things in my head at present so if anyone can help I'd much appreciate it

You thin until you recover the performance you are looking for and yes, you must put your normal bevel in after you've thinned unless you choose to change the type of edge you are producing (for example hamaguriba). You cannot really count strokes. You just go by angle and visuals and then by performance. If your bevels are too asymmetric, it will steer on you. If you don't mind the steering, then the bevels are symmetric enough. Go slow and check intermittently, if you want to go symmetric. I don't bother and go with a right hand bias, in general.

I'll give it a go in a few days when I'm off. Want to thin my JCK KV8 and if that is successful I'll do my Hattori FH at some point. I have a Naniwa 220 grit stone so hopefully it works ok, rarely use it any more

Keep in mind that thinning on a stone will convex your bevel. If you want it pretty flat, I would opt for a diamond plate and I wouldn't bother with an XXC. All diamond plates cut very, very fast. There is virtually no advantage to going with super coarse and you end up with gouges that take forever to remove.

I'll agree with tk, but will also point out that there are advantages to convexed bevels, so don't worry about that too much. Also, what you hit when thinning a knife is going to depend entirely on the original grind of the knife. Typically the best way to thin a knife is to lay it flat on the stone and put pressure opposite the edge. When this is done in most cases (unless the knife truly is flat ground from heel to spine) you will raise the spine off the stone a bit and only hit the bottom third of the blade face. This is where the "last 3rd" comes from.

Thanks for the replies fellas. I only have a few stones that hardly flashy but I'm definitely gonna use the 220 stone. I wouldn't mind a bit of convexity from my limited understanding of it, and diamond plates are silly expensive here anyways. My JCK KV8 is fairly thin to start so I hope I won't have to do much to notice a performance increase.

Another question. After I have thinned the knife to my satisfaction at 220 grit, I assume I just go through my normal progression of stones to polish the thinned part until the scratches are all gone from the previous grit? So most of the work is done at the lowest grit? And then after this is done I put a normal bevel on it again?

It all depends on what you want to do. What degree is your edge bevel now? How wide is the edge bevel (if the knife is truly thick then a high angle bevel will still be very tall - a good indicator that your knife is too thick). I personally like keeping the edge bevel at a low angle then adding a microbevel for strength on my highest grit stone. Either way, when you thin the knife you should see the edge bevel begin to disappear. If you want to get really intense with it, thin the knife until the current edge bevel is completely gone and then add a new edge bevel. This can tend to shorten the life of the knife though, so I'm not sure I'd suggest it. You can then go up through your normal progression if you choose (and I probably would to even up the scratches and get them down to a manageable size first), but it will probably still look pretty funky with the rest of the knife. If this bothers you, after taking it to a relatively high stone, go back with wetdry sandpaper and start at a lower grit (600 or so) and work your way up till you are pleased with the finish (usually 1500-2000 will do the trick). To me, it's not usually worth the effort, which is large.

At present the bevel on the knife is 10 degrees with a 15 degree microbevel and I noticed a decent improvement in that over the OOTB edge, hence I want to try thinning a little further. I don't wanna go overboard, just testing the waters if you follow me. I am not trying to turn a normal knife into a laser, I just wanna thin it a little to see how much of a difference it makes, and the KV8 isn't in my work rotation at present

Ok so I thinned the knife yesterday and it was a very interesting experience. One thing I noticed was that it seemed way easier to hold the angle on one side of the blade than the other. I'm a lefty so the right side of the knife is pretty scratched up, left not so bad. Guess it took about a couple of hours but I think it was worth it. I sorta ended up going a bit further than I had planned I think and thinned it a lot, but I was happy with the results. Even after 4000 grit the whole knife is pretty scratched up but I don't mind it that much

In terms of performance, the knife now cuts infinitely better than it did before. Not quite as well as my Masamoto or my Watanabe, but not far off considering it cost less than half of the Masamoto and nearly a third of the Watanabe. I tried the potato test Salty has been using and the knife performed very impressively, it seems there is a convex edge on it now as tk and UglyJoe predicted.

Overall I am pretty glad I did this. the KV8 only costs $145 and now that it is thinned and with the convex edge, it cuts incredibly well for all that it cost and it was definitely worth the effort